Does obstructive sleep apnea worsen during REM sleep?

Although it is thought that obstructive sleep apnea (OSA) is worse during rapid eye movement (REM) sleep than in non-REM (NREM) sleep there are some uncertainties, especially about apnoe-hypopnoe-index (AHI). Several studies found no significant difference in AHI between both sleep stages. However, REM sleep is associated more with side sleeping compared to NREM sleep, which suggests that body position is a possible confounding factor.